A keelboat is technically any sailboat with a keel—as opposed to a centerboard or daggerboard. In New Zealand the term keeler is frequently used as a generic alternative - meaning any sailboat with a keel, regardless of size.
ISAF (International Sailing Federation) usage differentiates keelboats (including the 12-meter class) from generally larger yachts, despite overlap in the sizes of boats in the two classes. The Olympic Games uses keelboat to describe keeled boats with up to a three-man crew, as opposed to larger-crewed boats such as the 12-metre class.
In some countries yachts can also be differentiated from keelboats with the addition of a toilet or "head" as the term "keelboat" is in some places understood to mean a sailboat with a keel that is designed purely for recreational/racing purposes, while the term "yacht" describes a sailboat designed for overnight transport.